1. Field of the Invention
The present patent application for industrial invention relates to a vehicle seat provided with compact fast-installing safety belt system.
The seat of the invention has been designed to overcome the drawbacks of the safety belt systems with self-adjustable height of the prior art that are embedded in the back of the seat.
More precisely, these seats have been designed to avoid positioning the recoil and restraint system of the safety belt in an external fixed framework, as it normally occurs in the majority of vehicles in which the entire system is anchored to the vehicle framework.
In particular, said seats have been particularly designed for coaches or buses in which seats are mounted in multiple rows and are not always provided with a fixed wall adapted to house the recoil and/or restraint systems of the safety belts.
Therefore the present invention falls within the sector of seats that embed guiding systems for seat belts with self-adjustable height in the back of the seat, which are able to adjust to the occupant's body size, and especially, height.
In fact, the guiding system for safety belts according to the invention is of three-point type (e.g. traditional system of car vehicles on the market), it being provided with two lower anchor points located on the two sides of the seat, and with a third deflection point located at the height of the occupant's shoulder.
Said third deflection point must be provided with a height adjustment device adapted to redirect the seat belt from one of the lower anchor points to the recoil and restraint device.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
The description of the prior art continues with reference to the EP1731385 patent registered on 03.03.2006 by FUNDACION INST TECHNO PARA SEG [ES] and claiming the priority of the Spanish patent application ES200400618 filed on Dec. 3, 2004.
The prior art is described with reference to FIG. 1, which is a schematic view of a guiding system for safety belts as described and claimed in the EP1731385 patent.
With reference to FIG. 1, the guiding system for safety belts comprises two lower anchor points (2 and 3), located on the two sides of a seat (1) and a deflection point (4) located at the height of the occupant's shoulder; said deflection point (4) is provided with a height adjustment device (5) adapted to redirect the belt web (7) from one of said lower anchor points (2 or 3) to a recoil and restraint device (9) that keeps the belt web (7) tight in normal conditions.
Said belt web (7) is diagonally positioned across the occupant's chest between the deflection point (4) and one of the lower anchor points (2 or 3) and is transversally positioned onto the lower part of the occupant's body between the lower anchor points (2 or 3).
The height adjustment device (5) of the deflection point (4) comprises sliding means (8) that are fixed to the vehicle bodyworks or to the relevant side of the vehicle seat and allow for freely positioning of the belt web (7) diagonally across the occupant's chest.
The innovative characteristic of said device was the provision of a second deflection point (6) fixed and arranged behind the vehicle occupant (10).
Moreover, means (8) are provided to allow freely displacement of the deflection point (4) of the safety belt web (7), redirecting the belt web (7) from a variable height that is automatically adjustable to the occupant's needs to the opposite side of the seat and to the second deflection point (6) wherefrom the belt web (7) is redirected to the supply and restraint device (9).
The first drawback of the system disclosed and claimed in the EP1731385 patent refers to the length of the belt web (7).
Being the recoil and restraint device (9) located in the lower part of the seat (1)—on the opposite side with respect to the deflection point (4)—said belt web is provided with a substantially vertical section (Y) going from the recoil and restraint device (9) to the deflection point (6) and a second substantially horizontal section (X) going from the deflection point (6) to the height adjustment device (5) of the deflection point (4).
Said first (Y) and second section (X) of the belt affect the total length of the belt web (7) and the size of the recoil and restraint device (9).
It must be noted that the cost of the entire system also depends on the total length of the belt web and on the dimensions of the recoil and restraint device (9).
Moreover, safety belts with insufficient length may be inappropriate for tall or heavily-built passengers.
The second drawback consists in the fact that, being said recoil and restraint device (9) located in the lower part of the seat-back and precisely on the seat, the total thickness of the seat-back is increased in a prominent point.
In fact, when the volume of the lower part of the seat-back increases, the distance between the front seat and the back seat must be modified in order to maintain the level of comfort unchanged for the passenger sitting on the back seat.
More precisely, said level of comfort depends on the distance between the seat of the back seat and the back side of the seat-back of the front seat, given the fact that the leg position of the passenger sitting on the back seat exclusively depends on said distance.
The EP 0 215 220 patent discloses a safety belt system comprising:                a first deflection point provided with height adjustment device, both being located on the side of the seat, in correspondence of the occupant's left shoulder;        a recoil device located behind the seat, in correspondence of the occupant's left shoulder; and        a second deflection point located behind the seat, in correspondence of the occupant's left shoulder, between the recoil device and the first deflection point.        
Therefore the first deflection point, the height adjustment device, the second deflection point and the recoil device are all located on the same side with respect to the occupant.
However the second deflection point consists in a “C”-shaped curved plate and the recoil axis of the recoil device is parallel to the plane of the seat-back. The structure and arrangement of the second deflection point and recoil device result in the additional extension of the belt and a high sliding friction, with the possibility that, when recoiling the belt, the belt section between the second deflection point and the recoil device may get twisted and blocked, thus jeopardizing belt operation and consequently passenger's safety.